Unbreakable Formation

Board-wide indestructible has always been a defensive line: a way to walk a token army through a wrath or shrug off an unfavorable block. What this spell adds is a second gear tied entirely to timing. Held up at instant speed, it does the reactive job cleanly: everything survives until end of turn, and you keep the ambush that go-wide white decks want as insurance against a sweeper. Cast it during your own main phase, though, and the Addendum bonus rewrites the equation: every creature grows, gains vigilance, and swings without leaving you defenseless behind. The counters are the reason the split matters. Indestructible and vigilance evaporate at cleanup, but the +1/+1 counters stay welded on, so the aggressive line is the only one that leaves a permanent dent in the board. That permanence is the whole argument for casting it forward instead of hoarding it as a trap. Note where the constraint lives: Addendum is an ability word, not a triggered ability, and it checks a single condition (whether you cast the spell during your main phase). Wait until you have attackers declared in combat and the bonus is gone entirely, because by then the main-phase window has closed. You lock in the pump before you know how the swing resolves. The reactive mode preserves the guessing-game tension white decks have always leaned on; the proactive mode nudges the same pilot to stop treating the card as a fog and start treating it as a finisher. One card serves both the aggressor closing a game and the defender who guessed wrong, and the decision belongs to the turn you cast it, not to deckbuilding.